How much do you weigh geared up? Im 250 plus gear (275 ish)?. 15-16 lbs rides great but in the rough, rocky stuff the rims and tires take a beating. I run at least 18 or higher usually and deal with the squirly ness in exchange for not having dented rims and pinch flats. I run in the rocky desert 90 percent of the time.

If you are 150-160 ish try 15 and 15 and go from there.

It might also depend on how heavy duty your tires are. DOT or Deserts have pretty stiff sidewalls and can .

If your front tire wants to slide out on ya lower the pressure. If the back one skips off of stuff rather than digs in, lower the pressure. If you can feel your rims getting knocked then raise it.

Dont forget that tire pressure can change as you ride. Maybe you are 17 or 18 in your driveway but after 20 mins on the highway you might be over 20?

I just press hard into the tires with the heal of my hand and gauge pressure that way. Gives me a feeling for what kind of hit it can take.

I just checked my factory service manual, Honda recommends 15 psi front and rear. When I worked at motorcycle dealerships in the late 80's-early 90's every dirtbike went out the door with 14 psi front and rear.

no isues with flats? seems a bit low for a heavy xr but Ill try it...
everybody else use these pressures pretty much?

Off road pressures I run are 12 front, 10 rear xr600r.
This gives you a great grip. Non dot dirt tires. I run in sharp rocks of the sierras and have to be aware of bashing. Never had a pinch flat, but have bashed the front good enough to "feel" that I should have been more careful over that particular terrain. My 92 front rim is no longer "true" due to bashing.

For the plated 91, I put 3000+ miles on a set of 606's. Tried different presures. Usualy ran at 18 street and trail, but no matter what those dunlops preductabley have an un-nerving slip inhearant to them. In the first 5 runs I ran the bike on, I almost crashed 3 times in off camber marble infested turns! SCAREY!
Now with mt21's at 20 F+R on the plated 91...big diff.
You can try creating slippage and still be comfortable with what they're going to do, which is very predictable and a really good grip. Tires make a big diff, pressure even bigger.

You've done it now. Ya just jinxed yer self. Get ready for a stream of flats.

yeah damn thats low, motocross style jaja

but if it works and gets the marbles off my tires Im all for it!

Way back when I used to weigh 145, lean and mean...NOW Im FAT marries and pig out all the time! AKA the good life! jajaja

si I weigh about 175lbs with gear...

I have an ac10 in the front(dont know if thats DOT and a t63 in the back which is DOT but has plenty stifness to it on the sidewalls. I also have an old inner tube to protect the inflated tube to prevent flats...old bike trick I used on MTBS...

anywhoo...

Ill try out these lower pressures...

Ill also put on my fork brace again...I noticed no difference in high speed fireroads but in the slow technical stuff I missed it quite a bit, also high speed on the highway it wont wallow as much...

I just checked my factory service manual, Honda recommends 15 psi front and rear. When I worked at motorcycle dealerships in the late 80's-early 90's every dirtbike went out the door with 14 psi front and rear.

BTW that's 12 in front, 10 in rear...
Have you checked your spokes?
Also aggresive riders should loft the front over sharp edges.
Still, no matter how you try to guard against it, sooner or later you WILL feel that you've hit something too hard. Motorcycle riding is an excersize in split second judgements.
As you ride, pick the best line, ease up, distribute your weight.

During outings I've had, when semi rookies complain of instabilities, we have them lower their tire pressures to the above specks and the squirrlyness goes away.
We do get to some rocky places so...we're not at high speed.

I sold off my second set of wheels, and the complete front end off my XR. Just waiting for my custom springs for the extra weight of the xr, and the cr500 swap is ready!!!!! I think I may need to get some new side panels and nice clean tank to match the new headlight and mx rear fender... can't wait to get it all together, snap some pics and go for a nice long ride!

Not sure what might be going on with your setup, but am installing XR650R forks on a few XR600/650L's right now, as well as a set of late-model CRF forks with CR500 triple clamps on another, and Javier at Trail Tricks was telling me that it's possible to build an XR650R / XR650L hybrid rear shock. Sounds similar to how we build CR500 hybrid shocks for the 650R's (and uses all of the leftover components from the hybrid 650R shocks - so can be a really cost-effective upgrade is you can find leftover parts).